The present disclosure relates generally to techniques for performing seismic operations about a subsurface structure. More specifically, the present invention relates to cable handling systems for deploying and/or retrieving seismic cable.
The exploration of oil and gas may involve the investigation of subsurface structures, such as geological formations and/or reservoirs. Seismic sensing systems may be positioned about a surface location for sensing properties of the subsurface structures. Such properties may include physical properties, such as pressure, motion, energy, etc. Such properties may occur naturally, or may be generated by imparting a force to the surface using a seismic energy source (e.g., a seismic vibration truck). The reflected seismic waves generated by the seismic energy source may be collected and analyzed to determine characteristics of the subsurface structures.
Techniques have been developed for sensing seismic parameters. Some techniques involve placing cable about a surface location near the subsurface structures of interest. Examples of such techniques are provided in US Patent/Application Nos. 20080062815, 20080060310, and 20080060311. The cable used in seismic operations may include sensors, such as optical sensors, geophone sensors and electronic modules, attached at intermittent points along a length of the cable. The sensors may have remote electronic monitoring packages that are linked to cables that carry each sensor's output signals back to a seismic recording system.
Some seismic sensing systems may be, for example, optical systems including seismic trucks distributed about a location for independently collecting seismic data. Each seismic truck may have fiber optic cables with optical sensors distributed about a surface location of a subsurface structure. The seismic trucks may also have a light source for emitting a laser through the fiber optic cables. The light source distributes light to and collects light from the optical sensors positioned along the fiber optic cables. The seismic truck may have devices for detecting changes in the light. Such changes may be used to determine information about and generate images of the subsurface structures. Examples of optical systems and sensors are provided in U.S. Pat. Nos. 7,622,706, 7,222,534, 7,154,082, and 6,549,488.
Seismic exploration of oil and gas reservoirs underlying land areas may require the laying and retrieval of lengths of seismic line cable. The cable may be carried to a given location and manually unwound from the reel for use. The cable may also be distributed using devices, such as the system described in U.S. Pat. No. 6,775,204. In applications involving the use of fiber optic cable, the optical sensors may be deployed with the cables. In some cases, the optical sensors may interfere with the devices used in distributing the cable or may be damaged during distribution. Thus, there remains a need to provide advanced techniques for deploying and retrieving seismic cable.